The present invention concerns a process for the manufacture of a foam body for installation in an ink cartridge of an ink jet printer. Such process is known from EP-A-709209. This specification concerns a three-color ink jet print head. These punched-out foam bodies are initially compressed in a heating press and warmed up, so that they settle down. Prior to installation, a jacket is placed around the foam body for the center chamber, which covers a portion of the lower surface and the two large surfaces of the foam body. The jacket consists, for example, of paper. The jacket facilitates the installation of the foam body in the relatively narrow and high center chamber.